When Paul and Victoria are looking at the view of Las Nubes, the sun is over the house (and therefore in front of them) in the shots of the house, but in the shots of them standing together, the light and shadows show that the sun is behind them.
When Paul goes to put the candy wedding band on Victoria's hand, he has a wedding ring on. Then he reaches back into the candy box for another band and puts it on and his original wedding ring is missing from his hand.
When presenting her with wedding ring from the candy box, three candies had "wedding bands" on them. After he removes one for her and one for himself, the remaining "wedding band" changes places in the box.
After the serenade Paul walks through the vineyard and away from the house. The moon is behind him and casts his shadow before him. He turns to look at the house and faces the moon. Now here is a bright light on his back (from the direction he was walking towards).
During the latter half of the grape-crushing scene when Paul Sutton is also in the large tub, Alberto Aragon and his wife Marie Jose stand behind it, cheering. Son Pedro Jr is just in front of them during the wide shots, but there's one close-up shot of the couple where Pedro Jr is suddenly absent.
As Paul is hitchhiking home south to San Francisco, a driver said he can take him as far as San Rafael. San Rafael is north of San Francisco. The car is also driving south (ocean to its right), which is correct. However, the coast is at least an hour out of his way to the west of Napa, and he would not have gone that way.